I guess you exported the 4D volume via QLab. Unfortunately, as far as I know, QLab still cannot export color Doppler images.
It is not just Philips, but all other ultrasound device manufacturers store most 3D/4D data in private fields and don’t give researchers free access (in fact, Philips is among the better ones by making at least Cartesian B-mode image export availalbe). We keep complaining to them that these limitations slow down research and ultimately hurt patients, but there has not been much effect so far. Please talk to your Philips representative about this, make it clear why data export is important for you. If many users request it then maybe they will do something.